1. Field of the Invention
The present invention relates to a commodity dryer for controlling the relative amount of moisture retained in the commodity and the surrounding atmosphere to not only dry but also to promote capillary action in the commodity to provide the optimum moisture to heat content of the grain by recirculating the air in the dryer and commodity bin while monitoring ambient conditions. More particularly the invention pertains to a commodity dryer which monitors the atmosphere of the commodity in relation to ambient temperature and storage bin heat transfer and depending upon the moisture requirements of the commodity may gradually introduce warm dry air into the top of the commodity bin while taking out moisture laden air from the bottom of the commodity bin or adding moisture to the commodity by adding moisture laden air to the top of the commodity bin. Moisture content of this air is controlled by passing the air through an evaporator heat exchanger coil which cools and thereby controls the amount of humidity in the air and transports the air to the condenser heat exchanger coil to pick up sufficient heat to gradually optimize the conditions in the commodity bin.
2. Description of the Prior Art
Various efforts have been made in the prior art and in the recent past to provide a commodity dryer to increase the storage life and quality of wheat, nuts, corn and other commodities in storage bins while maintaining the integrity of the vitamins, minerals, proteins, starches and sugars in the stored commodities. A practical commodity dryer has been required in agriculture since time immemorial since some years provide bumper crops of various commodities whereas some years due to draught and adverse growing conditions have produced inferior yields resulting in great fluctuations in the price of agricultural commodities.
There has been as a result numerous efforts to provide various types of commodity storage bins, grain elevators and the like to even out the years of bumper and lean crop production. The known storage devices have not solved the perennial problem since large masses of stored commodities have not been susceptible to prolonged periods of storage since the growth of fungus, bacteria and rot has resulted in a significant waste of agricultural commodities. The internal conditions of the storage bin are the net result of ambient temperature in conjunction with the condition of the commodity inside the bin and resulting heat transfers. These three factors many times combine to result in deleterious changes in atmospheric conditions around the mass of the grain causing all or part of the agricultural commodity to spoil.
In U.S. Pat. No. 2,661,603 a vault conditioner with control means is disclosed for controlling the relative humidity and temperature of merchandise storage vaults. This vault conditioner is described as being a self-contained machine constructed to meet the storage requirements of furs, foods, seeds and other products sensitive to water vapor and temperature. In operation, the vault conditioner withdraws air from the ceiling level of the storage room, cools it, reduces its humidity, and then discharges it at the floor level of the room. The invention as disclosed in U.S. Pat. No. 2,661,603 apparently utilizes convection current in assisting the action of the vault conditioner since the warmest air collects at the ceiling level from where it is withdrawn and returned to the cooling and dehumidifying unit for recirculation.
The commodity dryer of the present invention in contrast operates on an entirely different principle. The present commodity dryer creates a controlled atmosphere around the commodity by monitoring internal storage bin conditions and provides either moisture or dry air to provide the optimum conditions required for prolonged storage while preserving the nutritional value of the vitamins, minerals, proteins, starches, and sugars of the stored commodity. The internal conditions of the bin and grain as heretofore described are economically controlled as a result of a correlation of the internal conditions of the storage bin with the external ambient air conditions and resulting heat transfers. For example when a wet commodity is first stored in the present system, the commodity dryer adds dry air to the top of the commodity bin and removes moist humid air from the bottom of the commodity bin. The quantity of dry air added and the amount of wet moist air removed per unit of time depends upon the degree of moisture requiring removal to provide optimum storage conditions for the particular ambient temperature encountered in the storage location. The commodity dryer of the present invention may furthermore operate to provide both heat and dry air that is added to the commodity bin to dry wheat, corn, nuts and other grains stored in the commodity bin as it monitors the conditions both inside and outside the commodity bin to gradually optimize the conditions required for prolonged storage of agricultural commodities. The difference in design, function, and economic considerations of the present invention further translates into different arrangement and utilization of components to achieve the advantages of the invention. The present commodity dryer for example employs a compressor for driving an evaporator for cooling and removing moisture from the air and operating a condenser for thereafter reheating the dried air. The present unit further employs a hot/gas bypass for the efficient removal of ice from fins disposed on the evaporator heat exchanger coil where the commodity is in an extremely cold climate and/or is in an especially wet condition when stored.
The prior art has not provided a commodity dryer that will extend the life of stored commodities by controlling and gradually optimizing the atmosphere surrounding the commodity to yield after the removal of excessive moisture the optimum atmosphere necessary to prolong and preserve the vitamins, oils, minerals, proteins, starches and sugars indigenous to the condition of the particular stored commodity. The commodity dryer of the present invention is further designed to accomodate ambient atmospheric conditions at the site of the commodity dryer to provide the most efficient utilization of temperature and conditions for the removal or the addition of moisture to prolong the life of the stored commodity. The commodity dryer of the invention is further designed to coordinate outside temperature conditions with the internal conditions of the grain in the commodity bin to efficiently optimize the drying conditions of the grain in conjunction with the overall energy necessary to operate the system.